The monumental painting of St. Nicholas in the high altar of Ljubljana Cathedral, a work by the Venetian painter Pietro Liberi (1605–1687), was praised already in the late 17th century. However, in 1822 it was replaced with a new altarpiece and Liberi's fell into oblivion. It so happened that in 2004 the missing painting was found, which aroused great enthusiasm.
The almost four-metre high painting of St. Nicholas was mounted in the altar in 1674, after Bishop Josef Rabatta had added a Baroque sanctuary to the late-Gothic church. But the sanctuary, together with the entire old cathedral, was pulled down as soon as 1700 to give place to a new building, and Liberi's painting soon found itself in a new Baroque surroundings.
Bishop Rabatta comes from a family of Gorizian counts whose members were Austrian ambassadors in Venice. Therefore, it is possible to speculate on contacts with Venetian artists also in the light of these links. The first to mention explicitly the author of the painting was the Carniolan polymath Johann Weichard Valvasor in his comprehensive work The Glory of the Duchy of Carniola of 1689; he was of the opinion that the worthiest work to be seen in the cathedral was the painting by Liberi.
In 1822, Liberi's altarpiece was replaced with a painting of the same subject matter by the painter Matevž Langus (1792–1855), who in terms of composition relied largely on the Baroque predecessor. But merely twenty years passed when the variant by Langus was replaced with another canvas by him, but devised in a completely different manner. This painting was hanging in the high altar all until the return of Liberi's painting in December 2007.
What was the reason for replacing the well-preserved painting with a second-class work by a local painter? The answer can be found in the first variant by Langus in which the painter altered only the details that might have been questionable in the morally rigorous 19th century. Thus we can see that annoying on Liberi's canvas were the three adolescent angels in the upper portion of the painting who, watching idly the three saints below, erotically embrace one another. Langus replaced the sensually emphasized ephebes with cute little cherubs and added next to the figure of St. Nicholas an adult angel robed typically for the 19th century and holding the Saint's attribute, three golden balls. He literally repeated the two companions of the Saint, the holy bishop Hermagoras and his deacon Fortunatus, the traditional patron saints of the diocese of Ljubljana. The central figures in Liberi's painting stand on clouds, which agrees with the high position of the altarpiece, whereas in Langus's variant these figures stand on a stone pier by a rough sea, which is indeed related to the iconography of St. Nicholas.
For the watchful eyes and aesthetic standards of the Langus era also the static posture of the bareheaded Baroque Nicholas, with somewhat grotesquely oversized pontifical gloves, particularly the one on his blessing right hand, must have seem ungraceful. Most probably all the stated “indecencies” were the reason for the dethroning of the famous painting.
Although Liberi's painting was in a relatively good state of preservation, its restoration, carried out by the team of the Restoration Centre in Ljubljana, was a demanding job which, according to expert judgement, successfully led to full revival of the artwork, one of the chief attractions in the Baroque cathedral of Ljubljana.
When the Liberi piece was returned to its original place in the high altar in 2007, and the frescoes by Giulio Quaglio on the vast vault of the nave were also restored at the same time, Ljubljana Cathedral assumed again the character of a Baroque Gesamtkunstwerk, a total work of art, and thus its importance within the context of Baroque in Central Europe has considerably grown.